A number of developer solutions have been described for use with positive-working light-sensitive compositions such as photoresists and lithographic printing plates. Because alkaline solutions work so well with the quinone diazide compounds that comprise the majority of positive-working compositions, developers used have been primarily hydroxide solutions. Examples include tetramethylammonium hydroxide as described in British Pat. No. 1,367,830, published Sept. 25, 1974, and methyltriethanolammonium hydroxide as described in U.S. Pat. No. 4,141,733, issued on Feb. 27, 1979.
Another example of a useful hydroxide developer is tetraalkylammonium hydroxide as described for example in Japanese Publication No. 56226/76, published May 17, 1976. Such a developer comprises the noted quaternary ammonium hydroxide in an amount of from 1 to 2% by weight, wherein the alkyl portion has from 2 to 7 carbon atoms. The developer is said to be superior in a number of properties such as resolving power.
It has been found, however, that these developers tend to be deficient in developer selectivity--that is, the tendency of the developer to remove only the exposed portions of the light-sensitive composition and not any of the unexposed portions. To be useful, developer selectivity must be such as to produce a thickness loss in the unexposed portions that is no greater than 10% after development. However, losses approaching zero% are most desired. Such selectivity is important because it affects critical dimension control. That is, submicron dimensions of unexposed composition do not retain their tolerances if extended development has to be used. Extended development is the application of developer to the composition for a length of time in excess of the time needed for image clean-out. Such extended development is sometimes necessary in semiconductor fabrication, for example, if the resist is coated at varying thicknesses over an uneven substrate. In such cases the development used to clean out the thicker portions of the soluble resist cause the portions of lesser thickness to experience the extended development.
Particularly it has been found that a solution of greater than 1% by weight of (C.sub.n H.sub.2n+1).sub.4 NOH, wherein n is 2 to 7, has poor development selectivity, and is incapable of developing several useful positive-working resist compositions, even when used at reduced concentrations.